The presence of dopants within an insulating or semiconducting matrix can dramatically increase the electrical conductivity of the matrix. Dopants can be introduced into a matrix or moved within a matrix to dynamically alter the electrical operation of an electrical device. In some circumstances, the motion of dopants can be induced by the application of a programming electrical field across a suitable matrix. After removal of the electrical field, the location and characteristics of the dopants remain stable until the application of another programming electrical field. These changing dopant configurations within a matrix can be exhibited as changes in the electrical resistance of the device. The dopant configurations are a form of “memory” retained within the device which corresponds to past electrical conditions.
Devices which exhibit a “memory” of past electrical conditions are often called “memristors” or “memristive devices.” Memristive behavior is most strongly evident in nanometer scale devices and could potentially be used for high density data storage, circuit calibration, or to provide self programming, fuzzy logic, or neural learning capabilities. One of the fundamental challenges of implementing memristive devices is to integrate them with complimentary circuitry to perform high level tasks.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.